The present invention pertains to a device that controls power to an electric load. More specifically, the present invention relates to a sensor for detecting whether an area or room is occupied and detecting the level of ambient light in an area or room and activating lights or other apparatus accordingly.
There are a variety of sensors on the market that detect whether an area or room is occupied and automatically turn lights ON and OFF accordingly. These sensors commonly detect either movement in the room or body heat present in the room.
Movement is commonly detected by using an ultrasonic transmitter and receiver that are mounted in a room at a position where movement is most likely to be detected. The ultrasonic transmitter transmits an ultrasonic signal that reflects off objects in the room and is detected by the ultrasonic receiver. The frequency of the received waves can be used to detect movement by the Doppler effect. Body heat is typically detected by an infrared sensor that detects heat given off by a person in the room, or detects movement or changes in a heat source.
Despite the fact that these sensors are typically designed with an eye to energy efficiency, prior to the present invention, none of the available occupancy detector sensors were able to adjust the brightness of lights in a room according to the level of ambient light in the room. Thus, if it was a bright sunny day, the prior art occupancy detection sensors needlessly allowed energy to be consumed by turning lights ON to full intensity levels when lower wattage levels would have sufficiently lit a room.
Sensors that detect the level of ambient light in a room and either turn lights ON or OFF or adjust the intensity level of lights accordingly, to reduce the amount of energy consumed by the lights, are also available on the market. Although the primary purpose of these ambient light detector sensors is to ensure less energy is consumed, all of the currently available sensors adjust the brightness of lights in a room regardless of whether the room is occupied. Thus, the level of energy saved by using these sensors is not optimized, and energy costs are higher than necessary.